Foil.
An example of the element Polonium

Foil.
This is a very thin plating of polonium metal on gold foil, from Greg, who has been improving the quality of some of my element samples. He sells many unusual elements, including this one, on eBay: Check the Source link for more details.Source:Greg PContributor:Greg PAcquired:18 April, 2003Price: DonatedSize: 0.1"Purity: 99%